There are significant opportunities for developing low cost imaging modalities for localized cancer therapy monitoring and assessment that could serve to improve clinical outcomes. The principal hypothesis, which underpins this project, is that near-field microwave imaging can provide new forms of moderately resolved (5-10mm) spatial information which will positively influence clinical decision making in the therapy setting. The central themes for the proposed renewal period are (i) to complete the development and evaluation of 3D microwave imaging methods, (ii) to integrate ultrasound-heating technology with the imaging system, and (iii) to exploit the broadband spectral information in the acquired data. These themes lead to the hypotheses that (a) 3D methods are critical to accurate microwave imaging of tissue and can be realized in a practical form, (b) ultrasound heating technology can be integrated with the existing fixed array imaging design without compromising either the heating capabilities or the imaging performance, and (c) broadband spectral data improves data calibration, image reconstruction and tissue discrimination. The specific aims that will be pursued during the proposed continuation period to test these hypotheses are: (1) Development of 3D data acquisition, (2) Development of 3D image reconstruction which includes a number of advanced computational enhancement strategies, (3) Integration of the imaging array with scanned focused ultrasound, and (4) Experimental optimization of 3D microwave imaging using laboratory phantom studies and in vivo animal model systems to quantify static/dynamic imaging performance under conditions of therapeutic temperature elevation, thermally-induced lesions and ionizing radiation-induced reactions. If successful, this work would substantially advance the current state-of-the-art in medical microwave imaging technology paving the way for future studies at the clinical scale.